Workability and mechanical properties of microwave heating for recovering high quality aggregate from concrete

Microwave assisted concrete recycling is highlighted by a large number of research groups all over the world due to its potential for significant process benefit. In this paper, systematic experiments are established to investigate the heating process of mortar-aggregate under microwave irradiation. Four different aggregate types are selected that widely used as aggregates in concrete to represent different kinds of aggregates. The temperature field of both mortar and aggregate under different heating time and microwave power input are obtained. The crack formation, propagation and material damage during the heating process are graphically presented. XRD tests and SEM analysis are carried out to clarify the chemical content and microstructure variation around the aggregate-mortar interface before and after microwave heating. The mechanical properties of recycled concrete are evaluated through the UCS tests. Energy consumptions are tested during the heating process. The applications of microwave recovering aggregates from standard concretes are conducted based on the results obtained in the simplified concrete. The research proves that microwave irradiation could weaken the bonding between mortar and aggregate effectively, which provide a contribution and reference for the further application of microwave-assisted aggregates recycling.